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Lab 12A-1 Name: Section: Due Date: Climate Change Lab Before Coming to Lab: Read Chapter 16 (pages 491-525) in Thurman & Trujillo, 11th ed. The purpose of this lab is for you to familiarize yourself with climate change issues. You will begin by examining how the greenhouse effect works, how humans have affected the Earth’s atmosphere, and recent temperature data. Then, you will examine paleoclimate data from ice cores and consider its implications for the present global warming trend. Finally, you will consider how global warming will affect the oceans and humans. Names of Group Members: 1. 2. 3. Lab 12A-2 Stamps Activity #1: Carbon Dioxide in the Atmosphere Write your name in this box. Each square meter of the Earth’s receives about 240 Joules of heat from the Sun each second. The amount of heat received from the Sun is roughly the same as the amount of heat that is emitted (“sent away”) by the Earth out into space. Otherwise, the Earth would just get hotter and hotter and hotter over time. (If you receive heat, but do no lose heat, you get hotter.) The amount of heat emitted by a “black body” is given by the graph below. It is based on experiments done in laboratories: heat up an object, measure its temperature, and measure how much heat it gives off. (It will serve as an approximation for the how much heat the Earth emits.) le s Jo u infr are 24 0 le o ule s v is ib 24 0 J d The Earth must send away as much heat as it receives, or it will get warmer or colder. Sun 1. Based on the amount of heat that the Earth is emitting, what should the average temperature of the Earth be? __________________ Based on your own experience, does this result seem right to you? Is this the average temperature of the Earth? __________________ As you can see, this estimate appears to be wrong. We must have missed something and that something is, of course, the greenhouse effect. Most of the heat emitted by the Earth cannot pass directly through the atmosphere into space owing to greenhouse gases like carbon dioxide in the atmosphere that absorb infrared light, “trapping” its heat. 2. Why is the atmosphere’s “greenhouse effect” actually a good thing? (Hint: Think about what the Earth would be like if there were no “greenhouse effect.”) 3. What is the primary way in which humans increase the amount of carbon dioxide in the atmosphere? (Hint: What happens inside cars, power plants, etc?) Lab 12A-3 Examine the chart below. 4. Prior to the 1800s (the industrial revolution), was the carbon dioxide concentration in the atmosphere going up, going down, or fairly steady? _____________ Over the last century, has the carbon dioxide concentration in the atmosphere been going up, going down, or remained fairly steady? 5. Estimate the percentage increase in the amount of carbon dioxide in the atmosphere owing to human activities (i.e., since 1700). (Show your work. Be clear. Circle your answer.) _____________ Suppose that you invested $100 and later your investment was worth $110. What is the percentage increase in your investment? In fact, the amount of carbon dioxide in the atmosphere is a lot less than the amount of carbon dioxide that has been released into the atmosphere owing to the burning of fossil fuels by humans. A significant amount, about 1/3 to 1/2, has been absorbed by the ocean. We have no direct measurements of carbon dioxide in the atmosphere prior to the 1950s. However, when snow piles up at the Poles, it traps small amounts of air between the flakes, and these bubbles of air remain after the snow is compacted into ice. Scientists drill down into the ice sheets at the Poles and extract ice “cores” (like sediment cores). By counting down through the layers of ice (and other methods) and measuring the carbon dioxide in the air bubbles, scientists can estimate how much carbon dioxide was present in the atmosphere prior to the 1950s. 6. How can we test whether the carbon dioxide in the air bubbles of ice really does represent the carbon dioxide in the atmosphere at the time when the ice froze? Describe what you would do to test this idea using a device that could measure carbon dioxide in samples of air and ice. Hint: Examine the figure above. What do the circles mean? What does the line mean? Now compare them… Lab 12A-4 Activity #2: Local and Global Changes in Temperature Examine the graph below showing the average temperature each year at the Civic Center in downtown Los Angeles. 7. Prior to 1920, was the average temperature of Los Angeles going up, going down, or remaining fairly steady? _____________________________ After 1920, has the average temperature of Los Angeles been going up, going down, or remaining fairly steady? _____________________________ If the amount of carbon dioxide in the atmosphere has been going up significantly since the industrial revolution, then you might expect that the temperature everywhere, including Los Angeles, has been going up since that time as well (if carbon dioxide is really a significant contributor to the greenhouse effect). Clearly, this is not what the Los Angeles temperature record shows. 8. Does the one observation showing cooling in Los Angeles prove that global warming was not happening prior to 1920? Explain your reasoning. Hint: Suppose that you are a scientist given the task of determining whether or not global warming is happening: would you only measure the temperature at one location? 9. The local climate of a region is certainly affected by the amount of carbon dioxide in the atmosphere, but many other factors are also important: its latitude, whether it is close to or far from the ocean, the presence of mountains, etc. Global warming can cause shifts in other factors that also affect local climate. Aside from making things warmer, how could global warming affect local climate? Give at least 1 example of how global warming could cause a particular place to get colder, wetter (more humid), or dryer (less humid). Be as specific as you can. Lab 12A-5 Recent estimates of temperature are based on measurements from many places throughout the world. Unfortunately, we don’t have accurate measurements from many places in the world prior to the late 1800s. To determine the global temperature prior to this time, scientists have used temperature “proxies” to “reconstruct” the global temperature. (A proxy is someone who stands in for you to do something. For example, if someone takes your shift for you at work, they are your “proxy.”) Scientists use many proxies to infer temperature: tree rings, the layers and chemical composition of coral reefs, the chemical composition of fossils and ocean & lake sediments, etc. 10. Prior to the 1900s, was the Earth’s average temperature going up, going down, or fairly steady? Over the last century, has the Earth’s average temperature been going up, going down, or remained fairly steady? __________________ __________________ 11. In the graph above, the line shows the average temperature calculated using thermometer measurements from around the world. The circles show temperatures estimated using “proxies” (tree ring data, sea floor sediments, ice cores, coral reefs, etc.). How well do the temperatures based on proxies reflect the measured temperatures after 1900 (the time period where line and circles overlap)? In other words, are they about the same, and do they show approximately same upward trend? Does your comparison suggest that we can trust the temperatures estimated using proxies, or does it suggest that temperatures based on proxies are unreliable? Lab 12A-6 Activity #3: Changes in the Earth’s Climate in the Past Examine the graphs below showing the amount of carbon dioxide in the atmosphere and the temperature in the past. 12. Label the Ice Ages and “Warm Periods” in the figures above. Are we in an Ice Age or a “Warm Period” right now? __________________ 13. Describe the relationship – if any – between the amount of carbon dioxide in the atmosphere and temperature. Does your description support or undermine the idea that carbon dioxide is related to temperature by the greenhouse effect? _______________________ Lab 12A-7 The figure below shows the same temperature and carbon dioxide information displayed on the previous page but in a different format: a scatter plot. Each dot represents the global average temperature for a specific carbon dioxide concentration. As you can see, temperature tends to increase as carbon dioxide levels increase. 30.0 Temperature (degrees C) 25.0 20.0 15.0 10.0 5.0 0.0 150 200 250 300 350 400 Carbon Dioxide (ppm) 14. Amount of carbon dioxide currently in the atmosphere: (Use the figures in activity #1.) ________________________ Place an arrow (↑) on the carbon dioxide axis (x-axis) of the figure above at this value, and label the arrow “CO 2 now.” 15. Draw a line through the dots in the figure above representing the “trend” in the data. (In other words, draw a straight line representing the approximate slope of the data.) Label your line, “trend.” 16. Using the line, estimate the temperature at which the Earth’s climate will stabilize (stop increasing) if the trend holds true at the current, higher level of carbon dioxide (a big “if”): ________________ Place a dot in the figure at the temperature and carbon dioxide level. Label the dot “final global temperature.” 17. What is the “final global temperature” in degrees Fahrenheit? (Use the formula: [Temp. in oF] = 1.8 × [ Temp. in oC ] + 32oF ) The current average global temperature is about 60oF. If your estimate based on the past relationship between carbon dioxide and temperature is correct, how much will the average global temperature rise over the next few centuries? __________________ __________________ Lab 12A-8 Examine the graphs below showing the Earth’s “most recent” warming and the warm period before the last ice age. 18. Compare the current warm period with the last warm period (and the others in the previous graphs). How are they different? What is unusual about the current warm period? Remains of fossil humans that are anatomically like us (i.e., homo sapiens) show that humans have been on the Earth for at least a couple hundred thousand years. (My understanding is that scientists have difficulty determining whether many 200,000 to 500,000-year-old fossils are from homo erectus or homo sapiens: they are too similar.) However, human civilization (humans farming and building cities in places like ancient Egypt, Mesopotamia (modern Iraq), China, India, etc.) – is a very “recent” phenomena, say within the last 10,000 years. 19. A reasonable hypothesis is that civilization began about 10,000 years ago because the world’s climate became much more stable about 10,000 years ago. Why does civilization need a stable climate? In other words, what can hunter-gatherers do that city dwellers and farmers cannot easily do if the climate changes? Lab 12A-9 20. Estimate the rate (“how fast”) at which the world has gotten warmer over the last century. (In other words, what is the slope of the recent part of the temperature curve?) Answer in oC per year (oC /yr). (Use global temperature figure in activity #2.) (Show your work. Be clear. Circle your answer.) Recent Global Warming Estimate the rate (“how fast”) at which the world becomes warmer at the end of an ice age. (In other words, what is the slope of the temperature curve?) Answer in oC per year (oC /yr). (Use the figure on the previous page.) (Show your work. Be clear. Circle your answer.) Natural Global Warming (at the end of the last ice age) Divide your estimate of the “recent warming” by the “natural warming” at the end of the last ice age. How many times faster is warming over the last century than the fast, natural global warming at the end of an ice age? (Show your work. Be clear. Circle your answer.) Do your calculations support the idea that the recent warming is just a “natural” climate fluctuation and not related to human activities? Why or why not? (Select one answer from the list below.) • The recent global warming is much faster than the fast, natural warming that occurs at the end of an ice age, so the recent warming is unlike these previous natural warmings. Therefore, these calculations suggest that natural causes may not be sufficient to explain the recent warming and humans activities may be responsible. • The recent global warming is occurring at about the same rate as the fast, natural warming that occurs at the end of an ice age, so the recent warming is like these previous natural warmings and therefore natural causes may be sufficient to explain what is causing the recent warming. • The recent global warming is much slower than the fast, natural warming that occurs at the end of an ice age, so natural causes could explain and produce the recent warming because we know that they produced much larger ones in the past. Lab 12A-10 Activity #4: Global Warming and the Ocean 21. Why has the warming of the surface of the Earth been small even though a lot more heat has been added owing to trapping by greenhouse gases? Hint: Is the Earth mainly covered by land or ocean? How does it react to being heated? Consider your answer to the question above. If the temperature of the world only goes up a little owing to the extra trapped heat, then the Earth will only radiate a little more heat away as infrared “light.” In other words, more heat is still being trapped than sent away. Therefore, the world will continue to get warmer and warmer. This means that the ocean is only slowing down the warming; the Earth will eventually reach a much higher temperature at which it will be hot enough to send away as much heat as it receives from both the Sun and the atmosphere. 22. Will global warming cause global sea level to rise or fall? Why? (Give at least 2 reasons.) ________________________ (a) (b) 23. Will global warming increase or decrease the strength of hurricanes? In other words, will there be stronger hurricanes or weaker hurricanes? Why? ________________________ Lab 12A-11 24. How does the additional carbon dioxide in the ocean affect ocean life? As part of your answer, identify which organisms are affected and explain how or why they are affected. (a) potential benefits: Note: Discuss the effect of the carbon dioxide in the ocean water, not the additional carbon dioxide in the atmosphere or the warming of the ocean water. (b) negative effects: 25. (a) Will global warming increase or decrease the number of phytoplankton in the oceans? In other words, will there be more or fewer phytoplankton in the oceans? Explain your reasoning. Note: Discuss the effect of warmer water at the surface of the ocean, not the additional carbon dioxide in the atmosphere and ocean. (b) Will global warming increase or decrease the number of animals in the ocean? Explain your reasoning. Lab 12A-12 Humans have dumped more and more carbon dioxide into the atmosphere by burning fossils fuels like oil and natural gas, raising atmospheric levels by over 33% (a third), and as a result, more and more carbon dioxide has leaked into the ocean from the atmosphere. In fact, scientists estimate that the ocean absorbs somewhere between 33% and 50% of our carbon dioxide pollution. 26. Phytoplankton absorb carbon dioxide from ocean water, allowing the ocean to absorb more carbon dioxide from the atmosphere – but only if the carbon is not released back into the water (only if it is “permanently” removed from the ocean water). (a) Why does most of the carbon in phytoplankton bodies end up back in the ocean water? What happens to them as they sink toward the bottom (on their own or in fecal pellets)? (i) __________________________________________________________________ (ii) __________________________________________________________________ (b) The carbon in one body part is less likely to go back into ocean water. Which body part? What happens to the carbon in the body part? (In other words, if the carbon does not go back into the water, where does the carbon go?) (c) Suppose that there will be fewer phytoplankton in the ocean owing to global warming. Will the absence of phytoplankton help the world become even warmer, or help cool down the world? Explain your reasoning. Lab 12A-13 Activity #5: Thermohaline Circulation In the global thermohaline circulation, ocean water moves in giant loops called convection cells owing to changes in its temperature and salinity: “thermo” refers to temperature and “haline” refers to salinity. In this activity, we will begin to study the thermohaline circulation by examining how water’s temperature determines whether it floats or sinks. Begin the experiment by doing the following: • Fill the plastic bag with 3 ice cubes, and then add enough water to the bag to just barely cover the ice cubes. • Put the bag at one edge of the tank of water. Make it float as close as the surface as you can, and wrap the top of the bag over the edge of the tank so that it does not float away. • Let the tank rest for a minute or more so that the thermohaline circulation can establish itself. Then, add a drop of blue dye (next to the bag). Plastic Bag 27. Sketch the behavior of the dye into the figure on the right. Color the blue water into the picture, and draw blue arrows to show the motion of the water about a minute into the experiment. Add blue dye here Ice Cube 28. Describe the motion of the cold (blue) water in the tank in words. Add red dye here Lab 12A-14 The thermohaline circulation starts in certain special places near the Poles where water becomes dense enough to sink deep beneath the surface. As a result, warmer water flows towards the Poles at the surface to replace the water which sank. Once the water has sunk, the water slowly changes as the water mixes with neighboring water or via other processes (for example, oxygen is used up as animals breathe it in or bacteria use it to decompose sinking organic matter). As deep water warms owing to contact with the water above, it rises slowly over a broad area. (It gets lifted above colder water that sank more recently). The small amount which sinks quickly is exactly balanced by a large amount rising very slowly. Examine the side-view (cross-section) shown below. Ships traveled from India at the north end of the Indian Ocean all the way down to Antarctica and stopped occasionally to measure the temperature and other water properties deep beneath them. 29. Highlight the 2oC contour line (isotherm) in blue. Indian Ocean Temperature (degrees Celsius) Then, color all the water with a temperature less than 2oC in blue. 30. Add a a blue arrow to show the motion of the deeper water, and a red arrow to show the motion of the water near the surface of the ocean. 31. Where does the water sink, near Antarctica or India? Why does the water sink at this location? ___________________ Lab 12A-15 Scientists are interested in the thermohaline circulation for a variety of reasons. For example, the slowly rising water brings the deep, nutrient-rich water closer to surface, where wave orbitals can reach down and bring nutrients up to phytoplankton who live at the surface. In this lab, though, we will consider how the thermohaline circulation affects climate and life in the deep ocean. Antarctica 32. Sketch the currents of the thermohaline circulation into the side-view picture on the right, and label the surface currents as “warm” or “cool.” 33. Does the thermohaline circulation warm or cool the higher latitudes (“the Poles”)? _____________ How? Why? Explain. Examine the figure on the right. North Pole Equator CO2 lots of CO2 34. (a) How does the thermohaline circulation help the ocean absorb more carbon dioxide? little CO2 lots of CO2 Land (b) Does the thermohaline circulation make the world warmer or cooler overall? Why? How? ___________________________ Lab 12A-16 Activity #6: Winners and Losers from Global Warming 35. Is global warming a good thing or a bad thing? Your answer to this question probably depends on upon who you are. Are you a “winner” or a “loser”? In other words, will you benefit from global warming, or will it harm you? Consider whether global warming is a good or bad for the following people and organisms. Explain your reasoning. Actor Air Conditioner Manufacturer Ski Resort Employee Farmer in Canada Farmer in Mexico Dockworker on the Northern Coast of Russia Owners of Beachfront Property Diatom (a silica-shelled phytoplankton) Copepods (crustacean zooplankton) Good or Bad? Reasoning Lab 12A-17 Climate Change Lab (12A) Review: Hints & Advice Activity #1 To use the graph to estimate the temperature of the Earth, first determine how much heat the Earth is sending back into space as infrared light. Find this number on the y-axis, then go across the graph and place a dot on the curve at this value. Next, find the value on the x-axis that is below the dot. This is the temperature of the Earth – more precisely, this is the temperature that the Earth should have IF there were no greenhouse gases trapping the heat escaping from the Earth as infrared light. Do not forget to include the UNITS after every numerical answer. To calculate a percentage increase, divide the increase in the amount by the original amount. percentage increase = ( increase or “gain” ) / original amount For example, if you invested $100 and later it was worth $110, then your original investment of $100 has increased by $10, so the percentage increase is $10 / $100 = 0.10 = 10%. In question 6, the hypothesis is: “The proportion of carbon dioxide in air bubbles in ice is the same as the proportion of carbon dioxide in the atmosphere when the ice formed.” You need to propose an experiment that would test this hypothesis. You have equipment that measures carbon dioxide in the atmosphere and in bubbles in ice. All you need to do is to describe how you will use the equipment: When will you take samples from the air? From what layers of the ice will you take samples? When? Are any of the old observations of carbon dioxide in the atmosphere (the circles in the graph) useful to you? Activity #3 30.0 25.0 Temperature (degrees C) The “trend line” represents the slope of the data. The graph on the right shows several possible trend lines. Draw your trend line so that it goes through the data points “best” according to your own judgment. Your trend line does NOT need to go through “0.0” on the y-axis. 20.0 15.0 10.0 5.0 The temperature where the trend line meets the current level of carbon dioxide in the atmosphere is the (estimated) temperate that the Earth will eventually reach. 0.0 150 200 Do not forget to include the UNITS after every numerical answer. (Continued on the Next Page) 250 300 350 Carbon Dioxide (ppm) CO2 now (?) 400 Lab 12A-18 Civilization requires “cities” which require agriculture (farming) to support them, since (most) people are no longer hunters and gatherers roaming around looking for food. To calculate the speed at which the world is warming, you need to calculate the slope of the warming trends. Draw a line through the warming trend that represents the slope of the data “best” according to your judgment. Measure the “rise” and the “run:” the sides of the triangle of your trend line. The slope is the rise divided by the run: slope = ( rise ) / ( run ) rise run